Auto merge of #142911 - mejrs:unsized, r=compiler-errors

Remove support for dynamic allocas

Followup to rust-lang/rust#141811

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1492,12 +1492,6 @@ unsafe extern "C" {
         Ty: &'a Type,
         Name: *const c_char,
     ) -> &'a Value;
-    pub(crate) fn LLVMBuildArrayAlloca<'a>(
-        B: &Builder<'a>,
-        Ty: &'a Type,
-        Val: &'a Value,
-        Name: *const c_char,
-    ) -> &'a Value;
     pub(crate) fn LLVMBuildLoad2<'a>(
         B: &Builder<'a>,
         Ty: &'a Type,